This application claims the benefit under 35 U.S.C. xc2xa7119(e) of the U.S. provisional application No. 60/225,954 filed on Aug. 17, 2000.
1. Field of the Invention
The present invention relates to optics and, more specifically, to optical lenses.
2. Description of the Prior Art
The human eye 100, as shown in FIG. 1A, includes a cornea 102, an iris 104 that forms an aperture known as the pupil 106a and a retina 108 onto which light rays are focused. When the eye 100 is subjected to low ambient light conditions, the iris 104 dilates, resulting in a pupil 106a having a large aperture. If there is no spherical aberration in the cornea 102, then parallel light rays entering the eye 100 will be focused on a single point of the retina 108. If, on the other hand, the cornea 102 exhibits spherical aberration, as shown in FIG. 1B, the light rays will be focused over an area of the retina 108.
As shown in FIG. 1C, when an eye 100 without corneal spherical aberration views an object 110, light from each point (e.g., points A, B) along the object 110 are focused along corresponding points (e.g., points Axe2x80x2, Bxe2x80x2) on the retina 108, resulting in a clear image. This situation changes when the eye 100 has a spherical aberration, as shown in FIG. 1D. Light from each single point (e.g., point A) on the object 110 is directed to several points (e.g., points Axe2x80x2, Axe2x80x3, Axe2x80x2xe2x80x3), causing the object 110 to appear blurred.
This situation changes when an eye 100 is subjected to high ambient light conditions, as demonstrated in FIG. 1E. The iris 104 contracts, which results in the pupil 106e having a small aperture. Because light rays from an object 110 passing through the cornea 102 are constrained by the contracted pupil 106a, they tend to be highly focused on the retina 108. Thus, the object 110 appears in focus.
Therefore, there is a need for a lens that provides additional correction to a user when the user""s eye is subjected to low ambient light conditions, but that provides relatively less correction when the user""s eye is subjected to high ambient light conditions.
The disadvantages of the prior art are overcome by the present invention which, in one aspect, is a contact lens that includes a central zone and a peripheral zone. The central zone extends radially from a center to a central intermediate edge and has a radius corresponding to a radius of a contracted pupil of a user when subjected to a high ambient light condition. The central zone also has a constant first refractive power across the central zone. The peripheral zone extends radially from the central intermediate edge to an outer edge. The peripheral zone has a refractive power that is equal to the first refractive power at the intermediate edge and that changes radially and progressively toward a second refractive power, different from the first refractive power, at the outer edge.
In another aspect, the contact lens also includes a non-optical zone that extends radially from the outer edge to an outermost radius corresponding to a radius of a user""s cornea.
These and other aspects of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the following drawings. As would be obvious to one skilled in the art, many variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts of the disclosure.